The apparatus disclosed in Patent Document 1 below is known as an example of a conventional sterilization apparatus applied in a PET bottle (bottle made of polyethylene terephthalate) aseptic filling system. The disclosed apparatus is configured such that hydrogen peroxide mist is introduced into a PET bottle to sterilize the interior faces of the PET bottle, hot air is then pumped into the PET bottle such that the hydrogen peroxide mist floating inside the PET bottle is discharged to the outside, and then aseptic warm water is introduced into the PET bottle to clean it.